Transport cover, arrangement with a transport cover and with an electric machine and method for operating an electric machine

ABSTRACT

Transport cover (3), configured to be mounted to an electric machine (2), the electric machine (2) having a housing (4) with an end shield (5), a rotatable shaft (6) extending along a rotation axis (7) through the end shield (5) out of the housing (4) and a bearing (8) supporting the shaft (6) and mounted to the end shield (5), the transport cover (3) comprising a fixation section (11) fixable at the housing (4),a cover section (12) forming an accommodation space (14) for a stub (6a) of the shaft (6), anda through-hole (15) allowing to apply a lubricant from the outside of the transport cover (3) to the bearing (8) in a mounted state, in which the fixation section (11) is fixed at the housing (4).

Transport cover, arrangement with a transport cover and with an electricmachine and method for operating an electric machine

The present invention relates to a transport cover, configured to beattached to an electric machine. Besides, the present invention relatesto an arrangement with a transport cover and with an electric machineand to a method for operating an electric machine.

When manufacturing an integrated drive system with an electric machineand a gearbox attached to a housing of the electric machine, themanufacturing site for the electric machine may be different from amanufacturing site, where the gearbox is mounted to the electricmachine. In this case, the electric machine with its shaft extendingthrough an end shield of the housing has to be transported to themanufacturing site, where the gearbox is mounted. A correspondingintegrated drive system is e.g. known from DE 10 2015 218 856 A1, whichdiscloses an electric machine unit for an electric or hybrid vehiclehaving an electric machine that comprises a stator, a rotor shaft and anend shield with a bearing, that supports the rotor shaft, wherein theelectric machine unit comprises a gearbox section formed as a separatesection in axial extension of the rotor shaft.

It is an object of the present invention to provide a user-friendlytransportation protection for an electric machine.

According to the present invention, this object is solved by a transportcover, configured to be mounted to an electric machine, the electricmachine having a housing with an end shield, a rotatable shaft extendingalong a rotation axis through the end shield out of the housing and abearing supporting the shaft and mounted to the end shield, thetransport cover comprising a fixation section fixable at the housing, acover section forming an accommodation space for a stub of the shaft,and a through-hole allowing to apply a lubricant from the outside of thetransport cover to the bearing in a mounted state, in which the fixationsection is fixed at the housing.

Another aspect of the invention is directed to an arrangement,comprising the inventive transport cover and an electric machine havinga housing with an end shield, a rotatable shaft extending along arotation axis through the end shield out of the housing and a bearingsupporting the shaft and mounted to the end shield, the transport coverbeing mounted to the electric machine.

Preferably, the electric machine is configured to drive a vehicle, suchas a battery electric vehicle or a hybrid vehicle. Particularly, theelectric machine is capable of performing at least 10,000, 13,000, oreven 16,000 revolutions per minute. The electric machine may rotate upto 18,000 rpm. The electric machine may be an electric motor.Particularly, the electric machine is an induction machine or apermanently excited synchronous machine. The end shield may be a driveend (DE) shield of the electric machine. The electric machine may alsocomprise a further end shield being a non-drive end (NDE) shield mountedon a side being opposite to the drive end shield of the housing.Particularly, the end shield comprises a, particularly annular, axialrecess, into which the transport cover partially extends in the mountedstate.

The transport cover according to the invention allows to mount thetransport cover to the housing or the drive end shield whilemanufacturing the electric machine. When performing an end-of-line testof the electric machine, the lubricant, for instance, an oil can beapplied to the bearing without dismounting the transport cover.Additionally, the transport cover can remain in its mounted state whilerotating the shaft during the end-of-line test. Therein, the transportcover avoids that the lubricant splashes out of the electric machine andcauses dirt in a test area. After having performed the end-of-line test,the electric machine with the fixed transport cover the can betransported to a different manufacturing site, where a gearbox can beattached to the housing of the electric machine. During the transport,the mounted transport cover protects the stub of the shaft frommechanical damages and avoids effectively that the remaining lubricantleaks out of the electric machine.

Advantageously, the transport cover according to the present inventionintegrates the function of an anti-splash protection for the end-of-linetest and the function of a cover for transportation. Particularly incomparison to the use of an anti-splash being different from a cover fortransportation, a working step of cleaning the electric machine betweendismounting the anti-splash cover and mounting the cover fortransportation can be avoided, Thus, only a single cleaning step isnecessary at the manufacturing site, where the gearbox is mounted to theelectric machine, after removing the transport cover according to theinvention.

Preferably, the transport cover is configured to allow a rotation of theshaft inside the accommodation space in the mounted stage. Thethrough-hole may be surrounded by an annular section of the transportcover configured to extend away from the bearing in the mounted state.Preferably, the transport cover is made of plastic.

Preferably, the cover section has a radial recess that partiallysurrounds the through-hole. Providing the radial recess to the coversection simplifies applying the lubricant to the bearing because thethrough-hole can be positioned closer to the rotation axis and,therefore, closer to the bearing.

Preferably, the transport cover according to the invention furthercomprises a plate-shaped section, in which the through-hole is formed.Advantageously, the plate-shaped section provides a robust mechanicalbasis for forming the through-hole. More preferably, the plate-shapedsection extends into the recess of the cover section. Therein, theplate-shaped section can be completely or partially surrounded by thecover section.

Particularly, the plate-shaped section is configured to extendperpendicularly or substantially perpendicularly to the rotation axis inthe mounted state.

The transport cover according to the invention preferably comprises anattachment section configured to abut on the end shield in the mountedstate. Thereby, a contact face between the transport cover and the endshield is provided. Preferably, the attachment section has an annularshape.

Therein, the transport cover may further comprise a sealing member,preferably a sealing ring, configured to be attached between the endshield and the attachment section in the mounted state. The sealingmember improves the capability of the transport cover to prevent thatthe lubricant leaks out of the housing of the electric machine duringthe end of line test and/or during the transport.

Therein, the attachment section may have a cylinder-shaped member thatis configured to extend into the end shield in the mounted state,wherein the sealing member is arranged between the cylinder-shapedmember and the end shield.

Particularly, the recess of the end shield, the cylinder-shaped memberand the sealing member are arranged coaxially.

Furthermore, the attachment section may have collar section extendingaxially away from the housing in the mounted state. The collar sectionmay be formed to extend out of the recess of the housing in the mountedstate.

The plate-shaped may be formed integrally with the attachment section.Thereby, the transport cover can made smaller in axial direction.Particularly, the recess extends in axial direction until the attachmentsection.

Alternatively, the plate-shaped section may extend from the coversection, particularly may be spaced from the attachment section.

The cover section of the transport cover according to the invention mayhave at least partially the shape of a cone or truncated cone,Particularly, the cover section has the shape of the cone or thetruncated cone except in those parts, where the recess of thetransportation cover is formed, The cone or truncated cone shape allowsto form the accommodation space for the stub with a smaller diameterthan the bearing or the recess of the housing, respectively.

Alternatively or additionally, the cone may prevent that the lubricant,in particular an oil, flows back to the bearing. During end of linetesting, for instance, the lubricant, in particular the oil, may spreadinto the cone, and, due to the cone-shape of the cover section, may flowback to the bearing.

Preferably, the fixation section comprises two flange members eachconfigured to extend radially with respect to the rotation axis in themounted stage. The flange members preferably extend from the collar ofthe attachment section or from the cover section radially outwardly.

Additionally, stiffener members may be formed to the flange members andthe cover section.

With respect to the transport cover according to the invention it ispreferred that the fixation section comprises two fixation means thatare arranged such that an imaginary line between them does not intersectwith the rotation axis in the mounted state. In other words, thefixation means are arranged asymmetrically so that the transport coverhas an integrated rotation prevention and can be mounted only in aspecific alignment to the housing. Preferably, the fixation means arerealized by through-holes formed in the flange members.

Preferably, the transport cover according to the invention furthercomprises one or multiple fixation elements configured to fixate thefixation section by means of a snap-fit to the housing. Using a snap-fitallows to mount and dismount the transport cover easily by the workerson the different manufacturing sites. More preferably, the fixationelements are configured to be inserted into fixation means on thehousing of the electric machine, Particularly, the fixation means of thehousing are configured to fix the gearbox at the housing of the electricmachine after having removed the transport cover.

The transport cover according to the invention may further comprise aplug configured to close the through-hole. The plug allows to open andclose the through-hole easily for applying the lubricant. Preferably,the plug is made of rubber. The plug may comprise a sealing nose,particularly an annular sealing nose. The sealing nose can be broughtinto contact with the annular section surrounding the through-hole.

The object is further solved by means of a method for operating anelectric machine, the electric machine comprising a housing with an endshield, a rotatable shaft extending along a rotation axis through theend shield out of the housing and a bearing supporting the shaft andmounted to the end shield, the method comprising: mounting a transportcover according to the invention to the end shield such that the stub ofthe shaft is disposed in the accommodation space of the transport cover;applying a lubricant through the through-hole to the bearing; androtating the shaft in the mounted state of the transport cover afterhaving applied the lubricant.

Preferably, the method may comprise closing the through-hole by means ofa plug after having applied the lubricant through the trough-hole andbefore rotating the shaft in the mounted state of the transport cover.

The object is in particular solved by means of a method for operating anelectric machine, the electric machine comprising a housing with an endshield, a rotatable shaft extending along a rotation axis through theend shield out of the housing and a bearing supporting the shaft andmounted to the end shield, the method comprising:

-   -   mounting the transport cover to the end shield such that the        stub of the shaft is disposed in the accommodation space of the        transport cover,    -   applying a lubricant through the through-hole to the bearing,    -   closing the through-hole by means of a plug; and    -   rotating the shaft in the mounted state of the transport cover        after having applied the lubricant and dosing the through-hole        by means of the plug.

Preferably, oil is used as the lubricant. The electric machine, i.e. itsshaft, may be rotated with at least 10,000, 13,000, or at least 16,000revolutions per minute. The electric machine may be able to rotate up to18,000 rpm.

Using the cover, the electric machine with the cover mounted on isbetter protected, for instance, when transported. Particularly, afterhaving transported the electric machine and the transport cover in themounted state, the method according to the invention may furthercomprise the following steps particularly after having rotated theshaft: removing the transport cover; and mounting a gear box to theelectric machine.

All statements concerning the transport cover according to the inventionapply analogously to the above method, so that advantages described withregard to the inventive arrangement can be realized by the inventivemethod as well.

Further details and advantages are described in the following, whereinreference is made to the attached drawings. The drawings are schematicdrawings and show:

FIG. 1 a plan view on a first embodiment of the arrangement according tothe invention;

FIG. 2 a detailed perspective view on the transport cover according tothe first embodiment;

FIG. 3 a cross-sectional view corresponding to a sectional plane III-IIIin FIG. 1;

FIG. 4 a cross-sectional view corresponding to a sectional plane IV-IVin FIG. 1;

FIG. 5 a plan view on a second embodiment of the arrangement accordingto the invention;

FIG. 6 a perspective view on the transport cover according to the secondembodiment;

FIG. 7 a cross-sectional view corresponding to a sectional plane VII-VIIin FIG. 5; and

FIG. 8 a cross-sectional view corresponding to a sectional planeVIII-VIII in FIG. 5.

FIG. 1 to FIG. 4 show a first embodiment of the arrangement 1 with anelectric machine 2 and a transport cover 3, wherein FIG. 1 is a planview on the arrangement 1, FIG. 2 is detailed perspective view on thetransport cover 3, FIG. 3 is a cross-sectional view corresponding to asectional plane Ill-Ill in FIG. 1 and FIG. 4 is another sectional viewcorresponding to a sectional plane IV-IV in FIG. 1.

As shown in FIGS. 1 and 2, the electric machine 2 comprises a housing 4with an end shield 5 being a drive end (DE) shield. Furthermore, as canbe seen in FIG. 3, the electric machine 2 comprises a rotatable shaft 6extending along a rotation axis 7 through the end shield 5 out of thehousing 4 and a bearing 8 supporting the shaft 6. The bearing 8 ismounted to the end shield 5.

The electric machine 2 is intended to be attached to a separate gear box(not shown), which may be mounted by means of a flange connection to thehousing 4. Thereto, a plurality of fixation means 9 formed bythrough-holes may be provided in a flange section 10 of the housing 4.When the electric machine 2 is manufactured at a manufacturing site thatis different from the one, where the gear box is attached to theelectric machine, a stub 6 a (see FIG. 3) of the shaft 6, which extendsout of the housing 4, is protected from mechanical damages by means ofthe transport cover 3.

The transport cover 3 comprises a fixation section 11 that is fixable atthe housing 4 and shown in a mounted state, in which the fixationsection 11 is fixed at the housing. Furthermore, the transport cover 3comprises a cover section 12, which may have the shape of a truncatedcone as shown in FIGS. 1 and 2 and forms an accommodation space 14 forthe stub 6 a, as can be seen in FIG. 3.

Additionally, the transport cover 3 comprises a through-hole 15 thatallows to apply a lubricant, e.g. oil, from the outside of the transportcover 3 to the bearing 8 in the mounted state. In particular, thelubricant can be applied to the bearing 8 before an end-of-line test ofthe electric machine 2 before transporting it to the manufacturing site,where the gear box is attached. The transport cover 3 may remain in itsmounted state during an end-of-line test, so that lubricant, which hurlsaway due a rotation of the shaft 6 within the end-of-line test, cannotcause dirt outside of the transport cover 3.

For the present embodiment, the transport cover 3 comprises a plug 16made, for instance, from rubber. The plug 16 may comprise an annularsealing nose 17, and is configured to close the through-hole 15. Theplug 16 can be removed when applying the lubricant and close thethrough-hole 15 thereafter, particularly during the end-of-line test andthe transport.

As can be seen in detail in FIG. 2, the cover section 12 may have aradial recess 18 that at surrounds the through-hole 15. By providing therecess 18 the through-hole 15 can be positioned at a position thatcorresponds to the radial position of the part of the bearing 8, wherethe lubricant can be applied effectively. Moreover, the transport cover3 may comprise a plate-shaped section 19, in which the through-hole isformed and which extends into the recess 18. The plate-shaped section 19extends substantially perpendicularly to the rotation axis 7.Furthermore, the through-hole 15 may be surrounded by an annular section20 that extends from the plate-shaped section 19 into a directionopposite to the bearing 8. The annular section 20 supports the plug 16and forms a counterface for the sealing nose 17.

Preferably, the transport cover 3 also comprises an attachment section21 configured to abut on the end shield 5 in the mounted state. Thecover section 12 may extend from the attachment section 21 away from theend shield 5 in the mounted state. As can be seen in FIG. 2, in theaxial direction the recess 18 does not extend to the position, where theattachment section 21 contacts the cover section 12. Thereby, theplate-shaped section 19 may form a socket being axially displaced froman abutting position of the attachment section 21 in the mounted state.

A sealing member 22 of the transport cover 3 may be configured to bearranged between the end shield 5 and the attachment section 21. Theattachment section 21 may have a cylinder-shaped member 23 configured toextend into the end shield 5 in the mounted state, wherein the sealingmember 22 is arranged between the end shield 5 and the attachmentsection 21 in the mounted state. Exemplarily, the sealing member 22 isformed by sealing ring arranged in an annular groove 24 of theattachment section 21 or the cylinder-shaped member 23, respectively.Furthermore, the attachment section 21 may have an annular collar 25that extends away from the end shield 5 in the mounted state.

As can be seen best in FIG. 2 and FIG. 4, the fixation section 11 maycomprise two flange members 26, 27 each configured to extend radiallywith respect to the rotation axis 7 in the mounted state. In the presentembodiment, the flange members 26, 27 exemplarily extend from the collar25 of the attachment section 21. Also, the fixation section 11 maycomprise two fixation means 28, 29, each exemplarily formed bythrough-holes in a respective flange member 26, 27. As depicted in FIG.1, the fixation means 28, 29 may arranged such that an imaginary line 30between them does not intersect with the rotation axis 7 in the mountedstate. This asymmetrical arrangement of the fixation means 28, 29prevents that a worker mistakenly mounts the transport cover 3 turned by180° to the end shield 5, according to the concept of “poka yoke”.

Further, the fixation means 28, 29 may be arranged such that theirpositions match with the positions of two of the fixations means 9 ofthe housing 4. Thus, no additional fixation means beneath those forattaching the gearbox are needed to fixate the transport cover 3.

With reference to FIG. 2 and FIG. 4, the transport cover 3 may comprisetwo fixation elements 31, 32 configured to fixate the fixation section11 by means of a snap-fit to the housing 4. In the present embodiment,the fixation elements 31, 32 are configured to extend through thefixation means 28, 29 of the fixation section 11 into the fixation means9 of the housing 4 and to form a connection there.

The transport cover 3 may comprise a plurality of stiffener members 33formed with the cover section 12 and the fixation section 11. Thestiffener members 33 may be additionally be formed with attachmentsection 21. Further stiffener members 34 may be formed with theattachment section 21, particularly its collar 25, and the fixationsection 11, particularly one of its flange members 26, 27,

FIG. 5 to FIG. 8 show a second embodiment of the arrangement 1, whereinFIG. 5 is a plan view on the arrangement, FIG. 6 is a perspective viewon the transport cover 3, FIG. 7 is a cross-sectional view correspondingto a sectional plane VII-VII in FIG. 5 and FIG. 8 is a cross-sectionalview corresponding to a sectional plane VIII-VIII in FIG. 5. In thefollowing only the significant differences of the second embodiment incomparison to the first embodiment are described, wherein identical orequivalent components are provided with the same reference numerals.

According to the second embodiment the plate-shaped section 19 may beformed integrally with the attachment section 21, Therein, the recess 18may extend in axial direction until the attachment section 21.Furthermore, as it is apparent from FIG. 6 and FIG. 7, a collar ofattachment section 21 may be omitted. Moreover, the flange members 26,27 may extend directly from the cover section 12.

An embodiment of a method for operating the electric machine 2 isdescribed in the following:

As a first step the transport cover 1 according to any ofafore-mentioned embodiments is mounted to the end shield 5 such that thestub 6 a of the shaft 6 is disposed in the accommodation space 14 of thetransport cover 3. Next, the plug 16 may be removed from thethrough-hole 15. Then, the lubricant is applied through the through-hole15 to the bearing 8, Thereafter, the plug 16 may be disposed into thethrough-hole 15 so as to close it. As a next step the shaft 6 isrotated, e.g. with 14,000 to 18,000 revolutions per minute, in themounted state of the transport cover 3 in order to perform theend-of-line test.

When the end-of-line test is completed, the electric machine 2 and thetransport cover 3 in the mounted state may be transported. Particularlyafter the electric machine 2 has arrived at another manufacturing site,the transport cover 3 is removed. The end shield 5 may be cleaned fromremaining lubricant, if necessary, As a next step, the gear box ismounted to the electric machine 2.

1. A transport cover, configured to be mounted to an electric machine,the electric machine having a housing with an end shield, a rotatableshaft extending along a rotation axis through the end shield out of thehousing and a bearing supporting the shaft and mounted to the endshield, the transport cover comprising: a fixation section fixable atthe housing a cover section forming an accommodation space for a stub ofthe shaft; and through-hole allowing to apply a lubricant from theoutside of the transport cover to the bearing in a mounted state, inwhich the fixation section is fixed at the housing .
 2. The transportcover according to claim 1, wherein the cover section has a radialrecess that at least partially surrounds the through-hole.
 3. Thetransport cover according to claim 2, further comprising a plate-shapedsection, in which the through-hole is formed and which extends into therecess.
 4. The transport cover according to claim 3, wherein theplate-shaped section is configured to extend substantiallyperpendicularly to the rotation axis in the mounted state.
 5. Thetransport cover according to claim 1, further comprising: an attachmentsection configured to abut on the end shield in the mounted state. 6.The transport cover according to claim 5, further comprising a sealingring, configured to be arranged between the end shield and theattachment section in the mounted state.
 7. The transport coveraccording to claim 6, wherein the attachment section has acylinder-shaped member configured to extend into the end shield in themounted state, wherein the sealing ring is arranged between thecylinder-shaped member and the end shield.
 8. The transport coveraccording to claim 1, claims, wherein the cover section has at leastpartially the shape of a cone or of a truncated cone.
 9. The transportcover according to claim 1, wherein the fixation section comprises twoflange members each configured to extend radially with respect to therotation axis in the mounted state.
 10. The transport cover according toclaim 1, wherein the fixation section comprises two fixation means thatare arranged such that an imaginary line between them does not intersectwith the rotation axis in the mounted state, and/or one or multiplefixation elements configured to fixate the fixation section by asnap-fit to the housing.
 11. The transport cover according claim 1,further comprising a plug configured to close the through-hole.
 12. Anarrangement, comprising: a transport cover according to claim 1; and anelectric machine having a housing with an end shield, a rotatable shaftextending along a rotation axis through the end shield out of thehousing and a bearing supporting the shaft and mounted to the endshield, the transport cover being mounted to the electric machine.
 13. Amethod for operating an electric machine, the electric machinecomprising a housing with an end shield, a rotatable shaft extendingalong a rotation axis through the end shield out of the housing and abearing supporting the shaft and mounted to the end shield, the methodcomprising: mounting a transport cover according to claim 1 to the endshield such that the stub of the shaft is disposed in the accommodationspace of the transport cover; applying a lubricant through thethrough-hole to the bearing; and rotating the shaft in the mounted stateof the transport cover after having applied the lubricant.
 14. Themethod according to claim 13, further comprising: closing thethrough-hole using a plug after having applied the lubricant through thetrough-hole and before rotating the shaft in the mounted state of thetransport cover.
 15. The method according to claim 13, furthercomprising after rotating the shaft: removing the transport cover; andmounting a gear box to the electric machine.